The present invention relates to apparatus for extracting samples of material from flow lines or tanks, and in particular to a sampler which is specially adapted for extracting samples of dry powder or granular materials.
Various manufacturing operations require that the immediate or overall composition of a material flowing through a pipe or conduit be monitored. Such monitoring ordinarily is accomplished with apparatus denoted as samplers, which take samples of material from the main body thereof. When a composite sample of material is required, the apparatus may be operated to withdraw a series of small amounts of the material as it passes a sampling point, which individual samples are collected and represent a composite of the total volume of material.
Other uses for samplers are in on-line analysis applications in which the immediate composition of a material must be determined. For this application, the individual samples of material are not collected as a composite sample, but instead are separately analyzed.
To obtain the samples, some samplers continuously divert material from the flow lines or tanks, and from the diverted material the samples are removed in various ways. Attempts to withdraw small quantities directly from pipes or tanks, however, have presented many problems not altogether satisfactorily solved. For example, where material receiving holes or slots in samplers are adapted to be extended directly into a pipe, sampled material can build up in such holes and slots or in the sampler itself and either block the same or contaminate subsequent samples.
Sampling dry granular or particulate materials flowing in a conveying tube under the influence of a fluid such as air or by gravity is important in the day-to-day operations of many different types of manufacturing facilities and in the handling of various types of material as for processing. To remove the granular material sample from the sample collecting apparatus, in one aspect the art contemplates using some form of conveying screw to move the sampled material into registration with a discharge chute or port. While somewhat satisfactory, screw conveyor means for emptying the sampler nevertheless is susceptible to certain disadvantages due to the frequent maintenance required as a result of material becoming lodged between the conveying screw and the tube in which it is mounted.
In accordance with another known technique, a probe having an inlet opening is extended into a product flow so that the product enters the opening and fills the probe. After the probe is filled it is retracted to expose an outlet therefrom to a discharge port, whereupon air is introduced into the probe to blow collected material out of the probe and through the port. Although the technique is satisfactory if the nature of the material is such that it readily enters the probe inlet during sampling, in many cases it is difficult if not impossible to obtain a sufficient quantity of material in the probe for sampling purposes. In addition, although the art provides various types of samplers, they are usually specially designed for the particular type and environment of material to be sampled, and are otherwise lacking in versatility.